On Monday, May 05, 2014 at 07:47:30 PM, Wolfgang Denk wrote:
Dear Lukasz,
In message 1399295277-28334-1-git-send-email-l.majewski@samsung.com you
wrote:
The current approach set the initial value of crc32 calculation to zero, which is correct for calculating checksum of the whole chunk of data.
It however, lacks the flexibility, when one wants to calculate CRC32 of a file comprised of many smaller parts received separately.
In the proposed approach the output value is used as a starting condition for the proper crc32 calculation at crc32_wd function. This behavior is identical to the one provided by crc32() method implementation.
Additionally, comments were appropriately updated.
Signed-off-by: Lukasz Majewski l.majewski@samsung.com Cc: Marek Vasut marex@denx.de Cc: Simon Glass sjg@chromium.org
include/hash.h | 2 +- include/u-boot/crc.h | 3 ++- lib/crc32.c | 2 +- 3 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/include/hash.h b/include/hash.h index dc21678..abf704d 100644 --- a/include/hash.h +++ b/include/hash.h @@ -101,7 +101,7 @@ int hash_command(const char *algo_name, int flags, cmd_tbl_t *cmdtp, int flag,
- @algo_name: Hash algorithm to use
- @data: Data to hash
- @len: Lengh of data to hash in bytes
- @output: Place to put hash value
- @output: Place to put hash value - also the initial value
(crc32)
- @output_size: On entry, pointer to the number of bytes available in
output. On exit, pointer to the number of bytes used.If NULL, then it is assumed that the caller hasdiff --git a/include/u-boot/crc.h b/include/u-boot/crc.h index 754ac72..7a87911 100644 --- a/include/u-boot/crc.h +++ b/include/u-boot/crc.h @@ -19,7 +19,8 @@ uint32_t crc32_no_comp (uint32_t, const unsigned char *, uint);
- @input: Input buffer
- @ilen: Input buffer length
- @output: Place to put checksum result (4 bytes)
- @output: Place to provide initial CRC32 value and afterwards
put checksum result (4 bytes)@chunk_sz: Trigger watchdog after processing this many bytes
*/
void crc32_wd_buf(const unsigned char *input, uint ilen,
diff --git a/lib/crc32.c b/lib/crc32.c index 9759212..f6266c7 100644 --- a/lib/crc32.c +++ b/lib/crc32.c @@ -257,7 +257,7 @@ void crc32_wd_buf(const unsigned char *input, unsigned int ilen,
{
uint32_t crc;
- crc = crc32_wd(0, input, ilen, chunk_sz);
crc = crc32_wd(*(uint32_t *)output, input, ilen, chunk_sz);
crc = htonl(crc); memcpy(output, &crc, sizeof(crc));
This looks wrong to me, in a number of ways.
First, the *(uint32_t *)output cast, is likely to trigger unaligned accesses with the resulting problems on some platforms. Never, never ever cast a character pointer into something that requires any alignment!
Seconds, where exactly do you now initialize the CRC vlaue to start with 0 ?
Finally we should keep in mind (this is nothing caused by your patch, but when touching this area we really should consider it) that we have a number of (slightly) different CRC implementations thare cry for cleanup / unification: in addition to lib/crc32.c we have disk/part_efi.c (which provides efi_crc32()), drivers/mtd/ubi/crc32.c (which provides crc32_le() and crc32_be()), net/eth.c (which uses ether_crc()), we have BZ2_crc32Table[256] in lib/bzlib_private.h / lib/bzlib_crctable.c (which appears to be unsued), and we have tools/pblimage.c (which provides pbl_crc32()).
Just an addition ... All those different implementations should use the hash_*() calls and this one central implementation.
Thanks for pointing this part out.